This invention relates to a self-contained Energy Storage and Recovery System (ESRS) device for use in a vehicle, and specifically to an ESRS device comprising a high speed flywheel, i.e. a flywheel which can run at speeds greater than 20,000 revs, such as that disclosed in the applicant's patent no. GB2449117.
Currently known mechanical ESRS devices comprise a Continuously Variable Transmission (CVT) to transfer torque between the flywheel and the vehicle. The efficiency of torque transfer in a CVT-based ESRS device is dependent upon power, and only exhibits a high efficiency at high power levels.
An aim of the present invention is to provide mechanical ESRS devices comprise a Continuously Variable Transmission (CVT) to transfer torque between the flywheel and the vehicle. The efficiency of torque transfer in a CVT-based ESRS device is dependent upon power, and only exhibits a high efficiency at high power levels.
Accordingly the present invention provides, in a first aspect, an Energy Storage and Recovery System device as claimed in claim 1.
In a second aspect, the present invention provides a vehicle comprising a transmission shaft, wherein an ESRS device in accordance with the first aspect of the invention is mounted coupled to the transmission shaft.
An advantage of the present invention is that the multiple number of available gear ratios combined with the ability to slip clutches, provides a close approximation to the CVT of prior art embodiments, therefore resulting in a high round trip efficiency, for example of around 65% but with weight and cost savings. Furthermore, the device can change smoothly from one clutch to another, therefore eliminating the potential for torque discontinuity.
A further advantage of the present invention is that the device can be retrofitted onto current vehicles.
Furthermore, the efficiency of the torque transfer through the clutch-based transmission is completely independent of the power being transferred.
The device allows seamless transfer from one gear to another without torque interruption, and also negates the requirement for a gear change mechanism. Furthermore, the duration of the slip on each clutch is maintained at a short duration, thereby resulting in simpler thermal management.
Preferably the multiple clutches are wet mutliplate clutches, wherein a cooling oil flow is supplied to the centre of each clutch. The temperature of the clutches can thereby be maintained at an acceptable level, thereby prolonging the life of the clutches.
Preferably, a lubricant is supplied, via jets, to gear teeth as they come out of mesh, thereby controlling the temperature of the gear teeth, which would otherwise be high due to the high running speed of the flywheel, and also ensuring good lubrication.
Preferably each of the gears is located coaxially with a corresponding one of the gears and the respective clutch is a coaxially mounted wet, multiplate clutch located between the respective gears.
Preferably, the weight of the ESRS device is less than 20 kg, thereby optimising the efficiency of the vehicle into which it is fitted.
In a second aspect, the present invention provides a vehicle comprising a transmission input shaft, wherein an energy storage and recovery system device in accordance with the first aspect of the invention is coupled to the shaft.